Device for optically measuring light



Feb. 14, 1928.

yE. MAYER DEVICE FOR OPTIGALLY MEASURING LIGHT, PHOTOMETER Original Filed Aug. 27, 1923 TTOHNE Y'.

' By 7W reissued Feb. 14, 192s.

UNITED STATES `PATl-:NT OFFICE.-

EMIL MAYER, F VIENNA, AUSTRIA, ASSIGNOR T0 DREM PRODUCTS CORPBATIN, 0F NEW YORK, N. Y., A CORPORATION 0F NEW YORK.

DEVICE FOR OPTICALLY MEASURING LIGHT, PHOTOMETER.

Original No. 1,587,539, dated .Tune 8, 1926, Serial No. 659,456, led August 27, 1923, and in Austria April 28, 1923. Application for reissue filed April 27, 1927. `Serial No. 187,104.

My' invention relates to a new and improved exposure meter.

One'of the objects of my invention is to provide an exposure meter which will en- I able the 'user to readily and directly determine the exposure time and in addition the corresponding diaphragm'settingfor a still or moviecainera provided with a lens or ca liberedpinhole arid also for enlarging or reproducing appliances embodying lenses, so

that roper negatives or positives can be secured? Another object of my invention is to provide an exposure meter which can be operated directly for the above mentioned,L purposes, by means of light which istransmitted, retracted, reflected or is radiated from 4or emanates in any manner fromthe object to be photographed or reproduced.

Other objects of my inventionvwill be set forth in the following description and drawings which illustrate a preferred embodiment thereof, it being understood that the above general statement of the vobjects, of my invention is-intended merely to generally explain the same. v

Fig. 1 is a vertical section of one 'embodiment of my device, the upper part being shown in elevation.

Fig. 2 is a diagrammatic plan view showing one of the possible arrangements of the transmitting sections.

yFig. 3 is a view similar to Fig. 1 and shows a modification of my invention. t

Fig. 4 isayiew similar to Fig. 2 and 1t Shows the transmitting sections used in the second embodiment.

Fig. 5 is a detail( view of the second embodiment. v

Fig. 6 illustrates a third embodiment.

In/the construction shown in Figi, a number of light comparingsections la. of gradually varying translucency are provided. v

As shown in Fig. 2, these comparing sections may be arranged, side by side, although my invention is not limited to any particular arrangement of the said comparing sections. Each of these sections has an identifying 50 mark such as al numeral'or symbol formed thereon and a light contrast is provided between each section and its' identification, so that the identifying numeralor symbol is of glass or any other suitable material which is permeable'to light.- 'Of course, the comparing sections can be directly formed upon a sheet of glass of varying thickness or coloring so as to provide the requisite diference 1n light permeability. The comparing sections are mountedat the to of atube e Which is provided With an or inary iris diaphragm c. I, do not wish to limit my invenftion tothe use of an iris diaphragm as there are other known devices for regulating the hrightnessof the admitted light bundle, like Waterhouse stops, wedge-shaped slits, etc. Thisdiaphragm c is actuated by a ring m e out-line of the identifywhich can bemanipulated on the outside of the tube so as to open or close the diaphragm.

I have not shown the details of construction of the iris diaphragm o as this in itself is a well known piece of apparatus.

An indicator can be provided upon the rin m. to co-operate with any ordinary and we 1 known scale, so that the extent to which the diaphragm is opened canbe readily detcrmined, and expressed in customary terms.

A sheet of ground glass or othertranslucent material is located iii front ofthe diaphragm c so that the formation of an image within the apparatus, the so-called pin-hole effect, isprevented' when a diaphragm open` ing is very narrow. The tube e on which the comparing sections, the iris diaphragm and the outer sheet i are mounted, is slidably mounted within an outer 'tube d 'provided with an ordinary magnifying lens b. The usual. flaring end a is rovided'so as to proteot1 the eye of the oliserver from external li t.

glu the embodiment shown in Fig.` 1, 'a removable cover lc. is provided for the end of the inner tube e and this tube contains two sheets s made of glass or other transparent material lbetween which members of varying light permeability can be located. 5 This is for the purpose of subduing very bright light, or otherwise to regulate the brightness of the admitted light bundle.

In the embodiment shown inFigs. 3, 4; and 5, an inner tube 'n is located within the tube e. end of the inner tube n can be covered by an inner `o aque covering member o, which in this em odiment is shown as semi-circular, so that it covers half the aperture of the said inner tube n. The tube nv can be turned by means of a handle p which passes through a slot in the tube e. In this embodiment there are four-comparing sections h which are arranged as shown in Fig. 4, and as the inner tube n. is' turned4 by means of the handle p, the observer can exclude from the field of vision any of the sections h.

Inthe vembodiment shown in Fig. 6 the magnifying .lens is omit-ted and a tube d of any suitable length is provided in-which another tube e2 is slidably mounted. The light comparing sections can be provided by means of a translucent wedge c provided with identifying numerals for adjacent zones thereof. These adjacent zones are of different lightpermeability due to the diiference in thickness of the wedge at variousportions thereof.

In the embodiment shown in Fig.`6, any well known means equivalent to an iris diaphragm for regulating the size of the aperture through which 'i the light is admitted 'can be utilized, thus controlling the brightness of the admitted light bundle, by regulating the aperture.

The method of using follows: l

In the embodiment shown in Figs. 3-5, for example, the comparing section or field identified by the numeral 1/10 is the least permeable to light. Hence, this numeral, 1/10 for example, can only be observed when the light passing through this section corre- Spionds to sunlit outdoor subjects or the li e. If such light conditions are not present, then the numeral 1*/10 cannot seen by the observer. The sectio'nor field identified by the numeral 1/5 is somewhat more li ht permeable from the first mentioned section,

thi's'iapparatus is as the observer 'when sunlight iB Anotavailable, as on cloudy days. Similarly, the numeral V5 identifies a sec-tion which is more` light permeable than the second mentioned field. as for bright interiors, and the field identified v by the numeral 20 has a still greater light permeability, as for dark interiors.

The samerelationship exists in the yembodiment shownin Figs. 1 and 2.. In the embodiment shown 1n F1gs. 3 5,

Any desired port-ion of the inner` so that the numeral 1/54 can be seen by The observer will see only the numerals on those sections which are suiiciently illuminated by the said light, whose intensity varies according to the conditions present. For example. if the amount of light transmittedis such that the observer can seethe numeral 1/5, he will not be able to see the vnumeral 1/10, andv he will be able to see the numerals 5 and 20. The numeral 1/5, namely, the numeral corresponding to the field visible under the prevailing light conditions and having the smallest light ermeabilily, will identify to the observer the light conditions which are present. y

The iris diaphragm is then closed to its greatest extent or at least until the numeral disappears and'is then reopened until the observer can just see the identifying numeral which corresponds to the light conditions present. The aperture of the i iris diaphragm which vcan be readily indicated by means of a suitable scale, for example, the customary f scale, and the identifying numeral which indicates directly to the observer the light conditions which are present, enable him 4to immediately determine the amount of light which is necessary vfor securing the corresponding negative or positive. i i

For example, the identifying numeral for the field of smallest light permeability visible under the prevailinglight condition can correspond to the time of exposure -or the numeral can represent the frequence of 105 frames per second in movie cameras. which determines theexposure time, and the diaphragm setting. as determined by the position of the index at the moment of reap-` pearance of the numeral or symbol, can cor- 11' respond tothe diaphragm setting on the camera or -other optical apparatus which is being used. The user can secure the proper combination of exposure time and diaphragm setting, which regulates the amount of light action upon-the sensitive material.

,b v either adjusting the shutter speed or the diaphragm setting for the lens which is being used or both. In many cases the diahragm opening can be immediately adiusted with respect to the shutter speed or timing device so that the sensitive plate is acted upon by the proper amount of light uired for a correct exposure.

ccording to my invention the brightness of the 1i ht is measured by means of two combine and independently variable factors, namely, b a device which controls the admission of ight (such as an iris diaphragm) and a plurality of ields vof varyassociated with distinguishing marks. That is, according to -my invention the distinguishing marks are in the path of the bundle or' beam of light rays. This is an improved feature of my invention because due to the action of the human e e it is not possible to determine with su cient accuracy just when a transparent or translucent field becomes visible, when it is sufficiently illuminated. However, by directly associating a transparent or translucent field with some contrasting or identifying mark which is also illuminated by the beam of light, the necessary determination can be made with sufficient accuracy. I prefer to have the identifying markings such as 1/10 etc. directly indicate exposure time and to be directly located upon the said fields, but I do not wish to limit my invention to this feature as the said identifying marks are directly associated with the elds for the purposes of my invention, if the marks in the fields are, simultaneously illuminated in the instrument.

I have described a preferred embodiment of my invention, but it is clear that numerous changes and omissions could ,be made without departing from its spirit,

which is the combination of a plurality of.-

translucent fields selected lin accordance to the receptiveness of li ht sensitivel material with a device to regu ate the brightness of the admitted light bundle.

I claim y 1. In an exposure meter, the combination of a plurality of fields of varying lightpermeability, said fields being located .with- 1n the field of vision, each of said elds having an identifying mark thereon, adjustable means for regulating the brightnessvof the admitted light, and manually operated means for excluding selected fields from the line of vision of the observer.

2. A device according to claim 1 in which the said adjustable means consists of an iris diaphragm.I

3. In an exposure meter, the combination of .a plurality of fields of varying light ermeability, said fields heiner located with- 1n the field of vision, the said fields having ogaque faces and contrasting light ermea le identifying 'marks formed t ereon,`

means for controlling the brightness of the light which can be caused to pass through the said fields, and meansfor exeludin se-4A lected fields from the line of vision o the observer.

4. In an exposure meter, thecombination of a plurality of fields of varying'light of'a plurality of fields of, varying light`per- 60 meability .and having identifying marks formed thereon, said fields being located within the field of vision, manually operated means forexcluding selected fields from the line lof vision ofthe observer, and additionally manually controlled means for .regulating the aperture through which light passes to the said-fields.

5. In an vexposure meter, the combination 7o lpermeabi1ity,.said fields being located within the field of vision, each of said fields having an identifying mark thereon, an iris diaphragm associated with the said fields and.4 adapted to control the size of the aperture u through whichlight can pass through' the said fields, a sheet of translucent material associated with `the said diaphragm `and adapted to prevent the formation of an image in the device when the diaphragm opening is small, and manually operated means for excluding selected lfields from the line of vision of the observer. l

6. In an exposure meter having an aperture through which-li htis admitted, the combination of a plura ity of fields of varying light permeabilit said fields bein located Within vthe .fieldY of vision, and apted to be separately identified, means adapted to selectively expose said fields to the 9 beam of light rays, and adjustable means adapted to regulate the brightness of said beam of light in avsubstantially.continuous and uniform manner. I

7. In an exposure meter,the combination of aiplurality of fields of var ing light permeability, said fields -being ocated .within the field of vision, each of said fields having identifying means directly associated therewith in the device, means adapted to expose 10 said fields selectively-to the action of a. beam of light, and means adapted to regulate said beam of light.

8. In an exposure meter, the combination of a plurality of fields of varying light per- 105 meab1lity,.said fields being located within the field of vision, and adapted to be sepa.- rately identified by markings directly associated therewith, means adapted to selectively expose said fields to the action of a 11' beam of light, means adapted to .regulate said beam of light, and a sheet of .translucent material associated with said fields and adapted to prevent the formation of an image infthe device when a beamof light of 115 small diameter passes throuh the device.

-In testimony whereof I a x my signature. f

DR. EMIL MAYER. 

